In connection with pedestrian platforms, walkways, and sidewalks in locations such as subway or railway stations, loading docks, stages, speaking platforms, stairways, sidewalks, school crossings, airports, curb ramps, crosswalks and roadway crossings, etc. there is a requirement for pedestrians to be able to safely navigate and avoid hazards. The requirement is particularly acute in attempting to make such facilities accessible and safe for blind or visually impaired persons.
In the 1980's a series of studies were undertaken in the United States to improve the design of buildings and transportation facilities to improve the mobility of the visually impaired. These studies culminated in recommendations on making potential hazards detectable to the visually impaired either by use of the long cane or underfoot.
Americans with Disabilities Act (ADA): Accessibility Guidelines for Buildings and Facilities set the requirements for the use of detectable warnings to warn visually impaired persons of hazards. The Guidelines require that detectable warnings shall consist of raised truncated domes of prescribed diameter, height and center-to-center spacing and shall contrast visually with adjoining surfaces. Detectable warnings used on interior surfaces are required to differ from adjoining surfaces in resiliency or sound-on-cane contact. Various tactile tiles having raised truncated domes in compliance with the ADA Guidelines or the equivalent have been developed such as those shown in U.S. Pat. Nos. 4,715,743 and 5,303,669.